Commonly owned, copending application Ser. No. 09/107,620, filed May 3, 2000 and commonly owned U.S. Pat. No. 6,308,793 relate to an improved traction and suspension control assembly. The disclosures of this application and patent are hereby incorporated by reference.
This invention pertains to a traction and suspension control assembly associated with an air braking system for a tractor/trailer vehicle. The invention is particularly applicable to vehicles such as trucks/tractor systems known as a 6xc3x972 vehicle employing a traction control system with air suspension control transfer. It will be appreciated, however, that the invention may have broader applications and may be advantageously employed in related environments or applications.
1. Field of Invention
This invention pertains to a proportional control valve for a suspension assembly associated with an air braking system for a tractor/trailer vehicle. The invention is particularly applicable to vehicles such as trucks/tractor systems known as a 6xc3x972 vehicle employing a traction control system with air suspension control transfer. It will be appreciated, however, that the invention may have broader applications and may be advantageously employed in related environments or applications.
2. Description of Related Art
By way of brief background, a 6xc3x974 truck and tractor system employs a pair of drive axles. As will be appreciated, the vehicle cost associated with a pair of drive axles is substantially greater than a 6xc3x972 arrangement, i.e., a system in which only one of the two rear axles is a drive axle, because of the additional drive components. Since a 6xc3x974 system has increased weight, operating costs, complexity, maintenance costs, friction, and fuel consumption associated therewith, a 6xc3x972 assembly is highly desirable. On the other hand, a 6xc3x972 system has decreased traction capabilities relative to a 6xc3x974 configuration. Accordingly, a 6xc3x972 system using an air suspension control to transfer load to the drive axle has been proposed as a preferred arrangement that achieves enhanced traction control.
Generally, traction control systems employ similar principles to antilock braking systems on wet or slippery surfaces, curves, split surfaces, ice, and the like. Traction control assemblies sense when the wheels of a vehicle spin upon acceleration. This is representative of a loss of traction between the road surface and the tire. In response, drive torque is transferred to the non-spinning tires or wheels and a braking force is gently applied to the spinning wheel. This transfers the torque through the differential to the non-spinning, or more slowly spinning wheel. If both wheels spin, then the engine RPM is electronically controlled and reduced to an appropriate level.
As briefly indicated above, it has been proposed to shift or transfer the vehicle load in a 6xc3x972 arrangement. An air bag suspension assembly associated therewith reduces the suspension bag pressure in the non-drive axle so that more weight is transferred to the drive axle. In this manner, an increased portion of the load is transferred to the drive axle to enhance traction.
Prior systems allow for load transfer manually, i.e., via driver input, or automatically with wheel slip and the onset of an automatic traction event. Manual systems that allow for load transfer are cumbersome and always present the potential for mis-use by an operator. On the other hand, if load transfer occurs automatically only after a loss of traction, then some adhesion with the road surface is already lost. This loss of adhesion can make the vehicle more difficult to move.
Different driving conditions and different operator preferences require different traction control strategies. Thus, a need exists for a traction control system that can be operated in a plurality of operating modes based on vehicle operation, operator preference, or operating conditions.
To those ends, a system and method operative to enhance the traction of a vehicle have been developed. The system comprises a drive axle, a non-drive axle, a suspension assembly operative to support a vehicle load, and an actuator assembly operatively associated with the suspension assembly for selectively transferring a predetermined ratio of vehicle load from one axle to the other axle. The method comprises the steps of providing a suspension force to a suspension control assembly associated with the drive axle, providing a suspension force to a suspension control assembly associated with the non-drive axle and regulating the forces provided to the suspension control assemblies in response to a control signal so as to control an amount of weight born by the drive axle in a plurality of predetermined manners.
According to the present invention, a proportional load transfer valve shifts weight from a non-drive or tag axle to a drive axle in response to a signal from the traction control assembly during a traction event.
A principal advantage of the invention is the ability to control the load transfer of the weight from the tag axle to the drive axle for enhanced traction control.
Another advantage of the invention resides in the automated operation of the transfer that is responsive to a traction event.
Yet another advantage of the invention is found in the ability to selectively transfer weight to the drive axle under normal operating conditions in order to prevent a traction event.
A further advantage of the present invention is the ability to change traction control strategy based on vehicle operating mode, for example using a first strategy or mode when in a low gear and a second strategy or mode when in a high gear.
Still another advantage of the invention is found in the ability to limit the proportional load transfer.
Still other advantages and benefits of the invention will become apparent to those skilled in the art upon a reading and understanding of the following detailed description.